The present invention is concerned with brake apparatus for railway vehicles and particularly to such brake apparatus as disclosed in U.S. Pat. No. Re. 30,408 assigned to the assignee of the present invention.
In the above-mentioned Reissue patent, there is disclosed a dual-piston brake cylinder device that is arranged to provide for storage of sufficient air as necessary to develop the desired brake forces, without the need for conventional storage reservoirs. The dual pistons are tandem-connected, one being larger than the other and cooperating with the brake cylinder body to form air storage chambers on its opposite sides.
During brake release, air is supplied to these storage chambers by a control valve device that is operative in response to variations in the train brake pipe pressure. When a brake application is initiated, the control valve device connects air from one side of the larger piston to a corresponding side of the smaller piston. A one-way check valve device is provided to effect pressure equalization between the opposite chambers of the larger piston to permit movement of the dual pistons in a brake application direction under the influence of the pressure acting on the smaller piston. Once the tandem-connected pistons are in application position, the control valve releases pressure from the opposite side of the larger piston to establish a pressure differential thereacross and accordingly produce braking force.
The aforementioned transfer of air from the opposite side of the larger piston to the one side thereof, to maintain pressure equalization therebetween via the one-way check valve, tends to delay movement of the tandem-connected pistons to brake application position, however, and thus limits the brake-response time.